Wait. When did we start caring about how mods affect comfort or performance on this forum?
Cafe/customized bikes are some of the most uncomfortable things known to man. They make the seat a vinyl covered piece of metal and put it as far back as possible. Then, you remove all baffles and possibly eff the pipes all up and make it loud as hell and destroy the calculated backpressure (because nothing is quite as cool as hearing damage). Next, you put some big-ass ugly tires that will probably put you on your side the first chance you get. Of course, you also have to cut the back fender off (and maybe the frame) to get covered in mud and road-oil if it ever decides to sprinkle. Finally, you replace the handle bars with something that will allow you to put your hands as close to the front axle as you possibly can. Don't forget the pods either (but that is another thread).
So, you end up with a bike that wasn't fast (nor was supposed to be, its 40 years old...), now runs rough as a dirt road, sounds like a war zone, is as comfortable as riding on a rail, and possibly lacks basic road-worthiness equipment.
But it looks awesome. It's a piece of art straight out of your imagination. People give you respect cause they can't dream of have the technical knowledge or creativity to make it happen. Nobody calls you a moto-douche or lumps you in with the obnoxious squids on the highway. Nobody thinks you are an 55 year old account in midlife crisis (Harley's anyone?). Everyone turns their head, the chicks dig it, and you look like a total badass when you roll up.
If you want performance, go buy a BMW R1000s or something. For comfort, get a Goldwing. For bling, a Harley. But for style points, make a custom bike.
Carry on with the undertail exhaust. Even if it makes your seat hot, people pay a lot of money for an evenly tanned butt.